1. Technical Field
This Patent Disclosure relates generally to inductive sensing, such as may be used in measuring or detecting position, proximity or physical state or condition.
2. Related Art
Inductive resonant sensing is based on a resonant sensor that includes a resonator. The resonator is driven to operate at steady-state oscillation, projecting magnetic flux energy for sensing a conductive target. Applications include proximity or position sensing relative to the conductive target.
A resonant sensor includes a resonator, such as an LC tank circuit, characterized by a resonator frequency and resonator oscillation amplitude (resonance state). The resonator is configured for a nominal resonant frequency state (no target present), characterized by steady-state oscillation at a resonant frequency and resonant amplitude. For the nominal resonant frequency state, the resonator is driven with sufficient excitation to overcome inherent circuit losses such as coil resistance and lossy dielectric, which can be characterized as a resonant impedance (impedance at resonance).
For inductive sensing, magnetic flux energy projected from the inductive sensing coil induces eddy currents in a conductive target within a sensing range/area of the resonant sensor. Eddy current losses effectively change resonator impedance, resulting in changes in resonance state, as manifested by, for example, changes in resonator oscillation amplitude and frequency. This change in resonance state translates to a change in resonant frequency state relative to the nominal resonant frequency state, corresponding to a change in resonant impedance).